The present invention is directed to a magnetic field sensing device and more specifically to a twisted, ribbon-shaped strip of amorphous magnetic material which is supported in the twisted condition and exhibits an effect similar to a Wiegand effect.
A Wiegand wire is a bistable magnetic device having specific characteristics obtainable by processing a thin ferromagnetic wire to form a central relatively "soft" core portion and an outer relatively "hard" magnetized shell portion with relatively low and high coercivities respectively. Such a bistable ferromagnetic wire is disclosed in the Wiegand U.S. Pat. No. 3,820,090, granted June 25, 1974 and entitled "Bistable Magnetic Device". The magnetized shell portion is operable for magnetizing the core portion in a first direction, the magnetization of the core portion is reversible by application of a separate magnetic field and the shell portion is operable to remagnetize the core portion in a first direction upon removal of the separate magnetic field. As a result of the changing magnetic field, there is a net change in the flux outside of the wire and an appropriately placed pick-up coil will generate a pulse-shaped voltage having a peak value and a narrow width with no relation to the changing rate of the magnetic field. Thus, the Wiegand wire is useful as a magnetic sensor. However, a conventional Wiegand wire is capable of only being able to detect a fairly high external magnetic field.
German Offenlegungsschrift No. 28 06 249 discloses a transmitter for emitting an electrical signal during the magnetic reversal of a ferromagnetic wire within a coil wherein the wire is kept under tensile stress and/or torsional stress.